In the past, there has been an electrophotographic image forming apparatus. This image forming apparatus is generally initialized by uniformly charging a photoreceptor drum, forms an electrostatic latent image on the photoreceptor drum by optical writing, converts the electrostatic latent image into a toner image, that is, develops the electrostatic latent image, directly or indirectly transfers the toner image onto a transfer medium such as a sheet, and fixes the toner image with a fixing unit.
A developing unit is used to convert the electrostatic latent image into the toner image. The developing unit is provided with a developing roller that supplies toner to a photoreceptor drum, an auger roller that supplies toner to the developing roller while stirring and conveying the toner, and the like.
The toner present in the developing unit is a consumable that is consumed by development. When a sensor, a printed sheet counter, or the like detects that the toner present in the developing unit is equal to or smaller than a predetermined amount, the developing unit is replenished with toner from a toner replenishing container. The toner replenishing container, of which toner is used up and which becomes empty, is replaced with a new toner replenishing container.
Meanwhile, in the image forming apparatus for forming a color image, images are generally formed using, for example, four kinds of colors, that is, black, magenta, cyan, and yellow. For this reason, the image forming apparatus is provided with four kinds of image forming units. The image forming unit generally includes a developing kit and a photoreceptor kit.
In an early image forming unit, the developing kit is replaced with a new developing kit when toner of the developing kit is consumed and is used up. However, it is not easy to replace the developing kit. Accordingly, JP-A-09-50174 proposes a color electrophotographic apparatus in which a toner cartridge for replenishing a developing unit with toner is detachably mounted on the developing unit so that the developing unit can be easily replenished with toner for each color.
Meanwhile, generally, four kinds of toner replenishing containers (toner cartridges) corresponding to the developing kits (developing units) of the four kinds of image forming units have the same appearance and structure except that the colors of the toners stored in the toner replenishing containers are different from each other.
Since the toner replenishing containers have the same appearance and structure as described above, there was often a problem that, for example, a toner replenishing container storing a magenta toner is mounted on a connection portion connected to a developing kit developing a cyan toner image by mistake, or the like.
In order to solve such a problem, JP-A-2003-84534 discloses an image forming apparatus where incompatible identification devices are provided on toner replenishing containers and toner replenishing container-mounting portions provided on an apparatus body so as to correspond one to one. That is, there is proposed an image forming apparatus where incompatible “shape” or “mounting position” is set on a guide rail guiding a toner replenishing container to a mounting portion.
However, since a guide rail has different shapes or is provided at different positions on the four mounting portions for the toner replenishing containers in JP-A-2003-84534, an assembly process in a factory becomes complicated. In addition, an engagement groove, which is engaged with the guide rail, of the toner replenishing container also needs to have a different shape or be formed at a different position according to the kind of stored toner.
For this reason, since different molding dies are required for the toner replenishing containers corresponding to the kinds of stored toners, not only are costs increased but also space and effort are required for the inventory control of the toner replenishing container, which also causes costs to increase.